5. d2d3 As I wrote before, 4.a4 is a very small breath of fresh air. After 5.d3 we're back to hundreds of games, although this is better than the customary thousands. To be fair, many transpositions are still possible. 5... d7d6  6. a4a5 Following the principle, Whoever says A must say B. Or, paraphrasing it: If you play a4, you must play a5. 6... c5b4 The position is finally gaining independent value. 7. c1d2 